fix(android): fix deep links for keyman.com-based downloads

[jahorton]

As we've now internationalized keyman.com, placing a language code as the root path folder, we now need to accommodate this within the Android app for its deep links.

Fixes: #14854
Fixes: #16397

Build-bot: skip release:android

NOTE: The keyman.com support for deep-links only supports actual Keyman app releases and does not support local compilations properly. Per https://keyman.com/.well-known/assetlinks.json, it only supports the com.tavultesoft.kmapro package and not the com.tavultesoft.keyman.debug package. This made testing the fix more difficult than expected.

User Testing

GROUP_API_28: Perform these tests on devices with Android API 28 (Android 9).
GROUP_API_30: Perform these tests on devices with Android API 30 (Android 11).
GROUP_API_33: Perform these tests on devices with Android API 33+ (Android 13).

TEST_SEARCH_AND_TRY_DOWNLOAD: Using an emulated Android device with Keyman for Android installed, search for a keyboard package on keyman.com and attempt to download it.

• Within the emulated device's Chrome app, navigate to https://keyman.com and search for a keyboard of your choice.
• On the keyboard package's page, press the big green "Install Keyboard" download button.
• Keyman for Android should immediately launch, download the package, and start the package installer.

[keymanapp-test-bot]

User Test Results

Test specification and instructions

• ⬜ GROUP_API_28: Perform these tests on devices with Android API 28 (Android 9).

  • ⬜ TEST_SEARCH_AND_TRY_DOWNLOAD (OPEN)

• ⬜ GROUP_API_30: Perform these tests on devices with Android API 30 (Android 11).

  • ⬜ TEST_SEARCH_AND_TRY_DOWNLOAD (OPEN)

• ⬜ GROUP_API_33: Perform these tests on devices with Android API 33+ (Android 13).

  • ⬜ TEST_SEARCH_AND_TRY_DOWNLOAD (OPEN)

Results Template

# Test Results

### GROUP_API_28: Perform these tests on devices with Android API 28 (Android 9).

* **TEST_SEARCH_AND_TRY_DOWNLOAD (OPEN):** notes

### GROUP_API_30: Perform these tests on devices with Android API 30 (Android 11).

* **TEST_SEARCH_AND_TRY_DOWNLOAD (OPEN):** notes

### GROUP_API_33: Perform these tests on devices with Android API 33+ (Android 13).

* **TEST_SEARCH_AND_TRY_DOWNLOAD (OPEN):** notes

Test Artifacts

• Android
  • KeyboardHarness apk
  • KMSample1 apk
  • KMSample2 apk

[mcdurdin]

NOTE: The keyman.com support for deep-links only supports actual Keyman app releases and does not support local compilations properly. Per https://keyman.com/.well-known/assetlinks.json, it only supports the com.tavultesoft.kmapro package and not the com.tavultesoft.keyman.debug package. This made testing the fix more difficult than expected.

Yes, this is known to me. We could make the staging site support the debug package, but that's also a little tricky.

[mcdurdin]

This should not be needed -- see #16397 (comment)